The present invention broadly relates to the art of vehicle suspension systems and, more particularly, to a suspension system in which the spring rate, damping rate and ride height are adjustable to vary performance characteristics of an associated vehicle.
Embodiments of the present system find particular application for use in association with passenger vehicles, such as performance or sports-type coupes, for example. It will be appreciated, however, that the same or other embodiments are equally applicable for use in association with any other suitable types of vehicles, such as pick-up trucks, for example.
Suspension systems for vehicles are generally well known and commonly used. Typically, vehicles are originally equipped with a suspension system that balances two or more characteristics, such as ride comfort and road handling performance, for example. The suspension system of a vehicle is generally designed to emphasize some of these characteristics more than others, depending upon the style of the vehicle and the market that it is directed to. For example, a large sedan might have a soft suspension system that emphasizes ride comfort, whereas a sports car would likely have a relatively stiff suspension that prioritizes performance over ride comfort. In either case, however, the original suspension system of the vehicle still often remains a compromise between performance and ride comfort.
Given the balanced performance that is typically provided by the original suspension system of a vehicle, performance-oriented components are available that can be used to replace various parts or portions of the original suspension system to alter the handling characteristics of the vehicle. However, there are numerous problems associated with altering the performance of a vehicle in this manner. One problem is that different parts and components are selected depending upon the desired change in the level of performance. That is, different parts would be selected to upgrade the suspension system for increased performance on the road than would be selected for use of the vehicle on a race track, for example. Outfitting a vehicle with a suspension system that is well suited for the race track would likely give an undesirably firm or rough ride during an everyday commute. But, outfitting a vehicle with a suspension system that simply increases the handling characteristics of the vehicle over that of the original suspension will often provide insufficient performance when used on a race track. As such, modified suspension systems are often still a compromise between various levels of performance.
Another disadvantage of modifying the original suspension system of a vehicle by installing various performance-oriented components is that such modifications are time consuming and can be difficult for those without sufficient skill, knowledge and/or equipment. Furthermore, it is typically not practical to regularly switch between one set of components for use on the track and a different set of components for everyday driving. This is due, at least in part, to the time and effort required for such modifications.
Yet another disadvantage is that it is difficult to achieve optimum performance of a modified suspension system that is assembled using parts and components from various companies and manufacturers. Typically, there is little assurance of compatibility of these different components. Additionally, the replacement of some components without replacing others, and/or using a combination of unmatched or otherwise incompatible parts can result in a suspension system that does not perform as desired.
What's more, suspension systems provided as original equipment on vehicles typically are designed to deliver the same level of ride quality regardless of road conditions. That is, the original suspension system of a vehicle, such as a large sedan, for example, typically endeavors to provide the same ride and performance on smooth, straight highways as on rougher, winding country roads, for example. As such, the springs of original systems typically provide a relatively consistent spring rate through the entire stroke of the associated strut, damping member or shock absorber. One disadvantage of such springs is the inherent compromise of ride quality and performance, as discussed above. Another disadvantage is that such springs are not suitably adapted to provide selectively adjustable spring rates. As such, it is generally necessary to physically switch out the springs and replace them with other springs having a different spring rate. The disadvantages of having to switch out components are detailed above, i.e., skill, knowledge, equipment, etc.
Other springs that have a variable spring rate, which increases and decreases as the spring is displaced, are also well known and commonly used in suspension systems of vehicles. However, the spring rate of such springs is not actually adjustable. Rather, the spring rate of the spring gradually increases, due to the construction of the spring, as the same is compressed. Oppositely, the spring rate gradually decreases as the spring returns to its original height. Typically, the appropriate spring rate for the vehicle is selected for use at the intended height of the vehicle and is relatively constant throughout the normal range of travel or stroke of the associated damping members or struts. As the spring approaches the bottom of the stroke of the associated damper, the spring rate rapidly increases over a short distance to avoid or minimize the bottoming out of the suspension and the corresponding impact to the passengers of the vehicle. As such, changing the ride height of a vehicle typically does not significantly change the spring rate of the spring. In fact, in most applications to date, such a significant change in spring rate would be largely undesirable. As such, changing out the spring, as mentioned above, remains the only practical way to adjust the spring rate of known suspension systems.
Other known suspension systems are adapted, such as by using air springs, for example, to permit selective adjustment of the ride height of the associated vehicle. In addition to providing adjustment to the ride height of the vehicle, these systems are commonly used to automatically level the vehicle during dynamic operation thereof. While such features are well known and commonly used, these systems have certain problems and/or disadvantages that limit the utility of the same. One problem that has historically been associated with such systems is that forces on the struts or dampers, such as stiction and friction due to side loading, for example, cause the leveling to be inexact, such as by causing the system to undershoot or overshoot the desired suspension level. This, of course, is disadvantageous because repeated leveling operations are often required to level the vehicle as desired. What's more, these systems can also attempt to level the vehicle under certain conditions, such as when a vehicle is traveling along a curve, for example, that could result in an improperly leveled vehicle.